Prior art is limited to illuminators with speherical condensors and filters. These illuminators lack the advantage of conical beam concentrators in that they do not receive and emit parallel afocal beams. The beams received and emitted by concial lenses are parallel and afocal, and interference is reduced to a minimum.
The concentrated-beam illuminator is designed specifically for use with the Quadrant Conical-Lens Microscope, U.S. Pat. No. 4,469,411, issued Sept. 4, 1984, by this inventor. This microscope has eight 90.degree. longitudinal sectors of conical stage lenses which can be revolved into and out of the line of sight. A major disadvantage of the microscope is that the magnified image must pass through six lens surfaces in each stage, and this creates a problem of light penetration.
The problem of light penetration is partially solved by use of conical beam concentrators to increase the intensity of illumination. The beam concentrators are conical microscopic lenses disclosed in Conical Split-Image Microscopic Lens, U.S. Pat. No. 4,277,148, issued July 7, 1981, by this inventor.